Abstract:OBJECTIVE: To establish the pulmonary hemorrhage model in neonatal rats, which corresponds with the clinical etiology, and to explore its clinical significance. METHODS: Forty 4-7 day newborn Wistar rats were randomly assigned into four groups: one control group (Group A) and three hypothermia hypoxia groups. Group A rats were placed in an environment of 25℃, and the three hypothermia hypoxia groups were put into an organic glass box, the oxygen concentration of which was 5%-6%. The box was put into a refrigerator of (10±1)℃. According to the time of refrigeration, the rats were assigned into 1 h, 2 h and 4 h hypothermia hypoxia groups (Group B, Group C and Group D, respectively). They were taken out of the refrigerator after 1 h, 2 h and 4 h respectively and then were put into the organic water bath box within which the oxygen concentration remained 99.5% -100% for 2 h. After the rats were sacrificed, the degree of pulmonary hemorrhage was observed and then the gross anatomical findings were divided into five grades: Grade Ⅰ (normal lung), Grade Ⅱ (pulmonary edema), Grade Ⅲ (spotty pulmonary hemorrhage), Grade Ⅳ (local pulmonary hemorrhage) and Grade Ⅴ (diffuse pulmonary hemorrhage). RESULTS: ①There was no difference in the rectal temperature of the four groups before applying hypothermia, before rewarming and after rewarming. ②The pathologic changes of the lungs in Group A revealed Grade Ⅰ, Grade Ⅰ-Ⅲ in Group B, Grade Ⅰ-Ⅴ in Group C and Grade Ⅲ-Ⅴ in Group D. By the RIDIT analysis, a significant difference was found between Group C and Group D and between Group D and Group A, Group B or Group C (P< 0.05 or 0.01 ). ③Under the light and electron microscope, red blood cells were found in alveoli of the Grade Ⅲ-Ⅴ rats; the damage or breakage of the capillary basal membrane appeared in Grade Ⅳ-Ⅴ rats. These changes were found to correspond with the pathologic changes of neonatal pulmonary hemorrhage. CONCLUSIONS: The pulmonary hemorrhage model of neonatal rats, which corresponds to clinical etiology, can be established with 7 day newborn rats by rewarming and reoxygenating following hypothermia and hypoxia. The best effect comes from the group of hypothermia hypoxia for 4 h.
